dt-bindings: gpio: mpc8xxx: Convert to yaml format

Convert binding doc from txt to yaml.

Remove redundated "gpio1: gpio@2300000" example.
Add gpio-controller at example "gpio@1100".

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240531164357.1419858-1-Frank.Li@nxp.com


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>